Lead pencil, lead therefor, and process of making the same



Sept. 27, 1938. M. A..FERS T 2,131,657

LEAD PENCIL, LEAD THEREFOR, AND PROCESS OF MAKING THE SAME Filed Dec. 4,1936 Patented Sept. 27, 1938 UNITED STATES LEAD PENCIL, LEAD THEREFOR,AND PROC- ESS OF MAKING THE SAME Monie A. Ferst, Atlanta, Ga.,' assignorto M. A.

Ferst, Ltd., Atlanta, Ga., a corporation Georgia Application December 4,1936, Serial No. 114,291

6 Claims.

The invention relates to lead pencils, and has as an object theprovision of a lead pencil having the lead effectually interlocked withthe adhesive in the grooves of the sheath to prevent separation of thesheath and lead.

It is a further object of the invention to provide a lead pencil havingvthe lead interlocked with the adhesive and in addition having the fibersof the sheath reinforced about the lead.

It is a further object of the invention to provide a lead pencil havinga lead so formed that the adhesive will substantially entirely surroundthe lead when the pencil is assembled in the usual manner ofmanufacture.

It is a further object to provide a process of preparing leads forembodiment in lead pencils to secure the advantages of the invention.

It is a further object to provide a process of preparing the sheath tofurther secure the objects of the invention.

Further objects .of the invention will appear from the followingdescription when read in connection with the accompanying drawingshowing illustrative embodiments of the invention wherein-- t Figure 1is a side elevation of a pencil made in accordance with the inventionpartly broken away.

Figure 2 is an end view of parts of a pencil much enlarged, illustratingthe prior art.

Figure 3 is an end view of the pencil of the invention much enlarged.

Figure 4 is a detail section on line 4-4, Figure 3, showing the leadpartially in elevation.

Figure 5 is a side elevation of an old form of pencil showing the typeof fracture of the lead and its effect upon the Wood.

Figure 6 is a like view of a pencil of the invention.

The so-called lead of lead pencils is usually an extruded cylinderformed of a pigment, clay, and a waxy filler. is graphite. In coloredpencils a pigment of an appropriate color is substituted for graphite.In the present description and claims of the invention the popular termlead is used to include the marking element of lead pencils of anycolor.

In the manufacture of lead pencils it is the practice to prepare a blankof a width to provide a plurality of sheaths by forming parallel groovesto receive the leads, to place the leads in the grooves of one blank andapply glue to the surimmediately In black pencils the pigment face,including the grooves, of the complementary blank, and to thensuperimpose the two blanks.

The grooving of'theblanks is accomplished by means of cutters revolvingat high speed which has an effect of burnishing the surfaces of thegrooves, and the resultant smoothing and compression of the fibres closethe pores of the wood in such a manner as to interfere with access ofthe adhesive into the pores. I

. The present invention provides an added step in the preparation of theblanks by way of a roughening or opening of the pores of the wood at thesurfaces of the grooves. This may be ac- I complished in different ways.The surfaces of the grooves may be roughened by fine sand or emerypaper, by brushing with steel brushes, preferably revolving counter tothe direction of revolution of the grooving cutters, or the surfaces ofthe grooves may be sand blasted. At present the last named method ispreferred.

When the grooves are so treated, the adhesive, as glue,.is allowed toenter the pores of thewood and thus not only to provide a betterattachment of the leads but also to reinforce the fibers of the woodimmediately around the lead, the importance of which will be againreferred to.

An important feature of the invention relates to the preparation of theleads. It is well recognized in the art that the waxy constituent of theleads results in very poor bond between .the lead and the adhesive. Inan attempt to improve the bond between the lead and adhesive it has beenproposed to treat the lead by chemical means so as either to remove theWax from the surface or to deposit a substance, as calcium sulphate,upon the surface of the lead.

The pencil of the present invention comprises the usual grooved halfsheath I0 and ll the leads as shown at I2 and I3 being roughened bymechanical means to produce minute irregular indentations in the surfaceof the lead. Ob-

viously these indentations and the intervening depressions may be formedin any desirable manher but preferably by fracture of the surface of thelead breaking out minute portions thereof.

In the process of making lead pencils now in common use leads as H,Figure 2, are laid in one of the grooved blanks as by machinery and theonly glue utilized is applied to the surface of the remaining blank, asl6, and indicated in this figure at ill. The blanks are then superposedbut the glue obviously can not find its way between the lead It and theblank l5. It is impracticable by a machine operation to glue both of thesheaths. for the reason that the lead laying machine would becomesmeared and inoperative in a short time.

In accordance with the present invention the production of the pencilsknown to the trade as Rufinishiscarried out by the first step of rough 5ening the lead. This step in the process of making a'pencil causes aradical modification of the effects of each of the remaining steps forthe reason that when the leads [2 have been machine laid inthe halfsheaths II the surface between the lead and the sheath is not sealed,there being now a plurality of tortuous channels between the projectionscaused by communicating indentations and. as a resultwhen the step ofplacing the glue coated blank I upon the blank H and lead l2, the gluewill flow completely around the lead and interlock with the lead in amanner totally impossible with any structure of the prior art known toapplicant. The bond thus produced between the lead, and glue to the woodis such as to prevent the shattering fracture of the wood illustrated inFigure 5, but the lead will break either near or at the wood or ifpressuse is applied to a sufficiently short lead the wood will breakrelatively cleanly with adherence. completely about the broken offportion of thelead.

The roughening step of the process may also .be carried out in differentways. The lead may be acted upon by means of knurls, which in theiraction of revolution against the surface of the lead may produce groovesin a variety of directions preferably in the form of file teeth. ,The

lead may be provided by mechanical means with However it is at presentclosely spiralled ribs. preferred to mechanically act upon the leads bya sand blast while the surfaces of the leads are moving relative to theblast, or the blast nozzles are moved angularly relative to the leads,or both such movements are provided. When so sand blasted,.the particlesof sand will impinge upon the leads at various angles and the resultingminute pits will extend into the surfaces of the leads at various anglesso as to provide an effective interlock between the adhesive and the-lead.

A further unexpected result flows from this treatment. In the presentpractice of manufacture, the grooves are sought to be out upon aslightly larger radius than that .of the cylindrical surface of thelead. This for the reason that glue 5 or other adhesive is applied toonly one of the blanks and the slightly V-shaped recess between the leadand the sheath in which the lead is placed is expected to cause theadhesive to flow as nearly as possible entirely around the lead in theunglued blank. In practice however the grooving cutters soon becomeslightly worn at their corners so that the groove in a large number ofcases is really made semi-cylindrical closely fitting the lead, and theadhesive therefore en- 00 gages 'the lead on only one-half of itscircumference. 1

When the leads are prepared by the process of the present invention. theglue is enabled to flow from pit to pit entirely around the lead,thereby providing a complete bond between theadhesive and the lead.

When a lead pencil made in accordance with prior practice is sharpened,particularly upon a long taper, the sheath at the surface of the lead isreduced to a feather edge and in the absence of an effectual bondbetween the lead and the sheath, and particularly in the absence of anyreinforcing of the fibers in the feather edg the said fibers yield underpressure and the lead is broken off up into the sheath with crushing orsplintering of said fibers, thus necessitating a cutting away of aconsiderable length of the sheath before a new workable point is formedupon the lead.

When pencils are made in accordance with the present invention with thesaid fibers strengthened by being indurated by the adhesive, the fibersare enabled to resist said pressure and the leverage for breaking thepoint is only from the end of the said fibers to the end of thesharpened lead, and little trouble is found with the breaking of thelead up inside of the sheath. Comparative tests of pencils made inaccordance with the present invention and those of the best priorpractice show an advantage of substantially one hundred per cent infavor of the present invention;

Minor changes may be made in the physical embodiments of the inventionor ,in the steps of the process within the scope of the appended claimswithout departing from the spirit thereof.

I claim: v 1. In the process of manufacturing leads for pencils, thestep which comprises producing minute, irregular indentations in thesurface of the lead by mechanical action.

. 2. In the process of manufacturing leads for pencils, the step whichcomprises breaking out closely adjacent particles throughout the surfaceof the lead by mechanical means to produce a roughened surface thereon.

3. In the process of manufacturing leads for pencils, the step whichcomprises sand blasting the surface of the lead to form minuteadhesivereceiving indentations therein.

4. A pencil lead formed with a pitted surface of fracture with the pitsextending below an original surface of the lead.

5. A pencil lead formed at its longitudinal surface with closelyadjacent irregular eminences and depressions; a plurality of saiddepressions interconnecting.

6. A lead pencil comprising, in combination: a sheath; a lead formed atits surface with closely adjacent irregular eminences and depressions;and hardened adhesive surrounding the lead, projecting into saiddepressions and into pores of saidsheath to provide a mechanicalinterlock between the elements of the pencil.

' MONIE A. FERST.

